For hundreds of years artists, writers, politicians, and private persons have kept dairies. The diaries have generally been hand-written in a bound notebook on consecutive pages on which the date is either pre-recorded or is entered by the diarist as the entries are made.
This traditional method of keeping a diary has several useful features for the diarist and for subsequent readers. The diarist cannot easily go back and alter what he has written. Thus the diary is more likely a truer record of what the diarist actually thought at the time. The diary is "time stamped." The diarist may ink out or tear out pages, but it is clear to future readers that this has been done; the existence of an original record is apparent along with its mutilation to indicate the intent of the mutilator to destroy a particular entry.
Only a proportionally small amount of text can be inserted at a later date, and this can possibly be detected by changes in ink or slight changes in handwriting, or by the fact that the additions have been written in the margin. To the degree that these changes can be detected the diary is tamperproof.
Any reader of the diary can be sure by the handwriting of the identity of the person who wrote the diary; that is, the diary can be verified to be authentic. The diary may be locked away so that it is private.
Attempts have been made to provide a computer diary. Many such diaries are business oriented, designed to serve as reminders and not as permanent records.
The Tandy corporation has marketed a software product named "My Personal Diary" which allows the user to type into the dated image of a page of a diary. Although the software controls access to the diary pages by use of passwords, it is possible for anyone with access to use the software to turn to any date in this diary, past, present, or future, and to delete and enter data at will. This is very unlike a real personal diary in that there is no way to determine if an entry for any date was written at any time close to that date or was written or changed months or years later.